Selection between two different coding schemes and corresponding modulation schemes according to the allowable transmission delay of the data

ABSTRACT

Transmitters comprising detectors ( 32 ) for detecting packet data to be transmitted are provided with selectors ( 34 ) for in response to detection results of real-time requirements selecting first coding schemes and first modulation schemes like convolutional codes and adaptive orthogonal frequency division modulation schemes and for in response to non-real-time requirements selecting second coding schemes and second modulation schemes like turbo codes and orthogonal frequency division modulation schemes, to transmit with increased efficiency. Further detection results comprise target bit error rates and/or a payload bit rates, and further detectors ( 33 ) detect channel conditions. A processor system ( 20 ) runs adaptive algorithms for evaluating a maximum available bit rate in dependence of said channel conditions and/or margin adaptive algorithms for computing a bit loading in dependence of an actual bit rate. A code rate adapter ( 35 ) adapts code rates for said computing, and a generator ( 36 ) generates code rates and/or block lengths and/or numbers of iterations and/or code parameters.

The invention relates to a transmitter for transmitting packet data andcomprising a detector for detecting packet data to be transmitted.

The invention also relates to a processor system for use in atransmitter for transmitting packet data and comprising a detector fordetecting packet data to be transmitted, and to a method fortransmitting packet data and comprising the step of detecting packetdata to be transmitted, and to a processor program product for use in atransmitter for transmitting packet data and comprising the function ofdetecting packet data to be transmitted.

Such a transmitter forms for example part of a transceiver fortransmitting and receiving packet data, which transceiver for exampleforms part of a mobile phone or a base station or a node or a wirelesslocal area network or a wireless unit etc.

A prior art method for transmitting packet data is known from US2001/0010687, which discloses the detecting of a service option of apacket and in response allocating a control channel or a traffic channelfor said transmitting.

The known transmitter is disadvantageous, inter alia, due to not usingchannels efficiently.

It is an object of the invention, inter alia, of providing a transmitteras defined in the preamble which uses channels more efficiently.

The transmitter according to the invention is characterized in that saidtransmitter comprises a selector for in response to a detection resultof a real-time requirement selecting a first coding scheme and a firstmodulation scheme for coding and modulating said packet data and for inresponse to a non-real-time requirement selecting a second coding schemeand a second modulation scheme for coding and modulating said packetdata.

Said selector selects the coding scheme and the modulation scheme forcoding and modulating said packet data dependently upon said packet datahaving a real-time or non-real-time requirement. As a result, fordifferent requirements, the best coding scheme and modulation scheme canbe chosen per requirement.

The invention is based upon an insight, inter alia, that packet datahaving real-time requirements and packet data having non-real-timerequirements should be treated differently, and is based upon a basicidea, inter alia, that these different requirements can be detected,with the detection result defining the best coding scheme and modulationscheme.

The invention solves the problem, inter alia, of providing a transmitteras defined in the preamble which uses channels more efficiently, and isadvantageous, inter alia, in that packet data is transmitted at improvedefficiency.

Said detector and said selector for example form part of a processorsystem. Said packet data comprises one (art of a) packet or more (partsof) packets etc., and said coding scheme and modulation scheme areselected per time slot or group of time slots or (part of a) frame etc.The real-time requirements and non-real-time requirements can forexample be detected by detecting the kind of traffic to which saidpacket data belongs, like for example audio, video, data etc.

A first embodiment of the transmitter according to the invention asdefined in claim 2 is advantageous in that said first coding schemecomprises a convolutional code and said first modulation schemecomprises an adaptive orthogonal frequency division modulation schemeand said second coding scheme comprises a turbo code and said secondmodulation scheme comprises an orthogonal frequency division modulationscheme.

Said convolutional code and adaptive orthogonal frequency divisionmodulation scheme allow the transmission of packet data having real-timerequirements with improved efficiency, and said turbo code andorthogonal frequency division modulation scheme allow the transmissionof packet data having non-real-time requirements with improvedefficiency.

Orthogonal Frequency Division Modulation or OFDM is a multi-carriermodulation scheme, in which each sub-carrier is modulated with aM-Quadrature Amplitude Modulation or M-QAM. If M has the same value forevery sub-carrier it is a standard OFDM. If M can adaptively varysub-carrier per sub-carrier it is an Adaptive OFDM or AOFDM. Due to theperformance of turbo codes+OFDM and the performance of turbo codes+AOFDMbeing rather similar, turbo codes should be used in combination withstandard OFDM. Turbo codes cause delays, that's why under real-timerequirements the convolutional codes are to be used.

A second embodiment of the transmitter according to the invention asdefined in claim 3 is advantageous in that a further detection resultcomprises a target bit error rate and/or a payload bit rate.

Said detection of the target bit error rate and/or of the payload bitrate is used to advantageously improve/adapt said coding scheme and/ormodulation scheme. The real-time/non-real-time requirements and thetarget bit error rate and the payload bit rate all belong to thecollection of quality-of-service parameters or QoS parameters, togetherwith for example the maximum delay and the maximum time jitter etc. So,generally, a first QoS parameter is detected for making a firstselection, and a second QoS parameter is detected for making a secondselection etc.

A third embodiment of the transmitter according to the invention asdefined in claim 4 is advantageous in that said transmitter comprises afurther detector for detecting channel conditions.

Said detection of the channel conditions like for example the signal tonoise ratio level or SNR level is used to advantageously improve/adaptsaid coding scheme and/or modulation scheme. In case of stable channelconditions, said improving/adapting could be done less, and in case ofunstable channel conditions, said improving/adapting should be done moreoften.

A fourth embodiment of the transmitter according to the invention asdefined in claim 5 is advantageous in that said transmitter comprises aprocessor system for running an algorithm.

Said algorithm will improve/adapt said coding scheme and/or modulationscheme and/or will support the detecting of channel conditions and/orprocess the channel conditions.

A fifth embodiment of the transmitter according to the invention asdefined in claim 6 is advantageous in that said algorithm comprises arate adaptive algorithm for evaluating a maximum available bit rate independence of said channel conditions.

Said maximum available bit rate indicates the maximum number of bits pertime slot or group of time slots or (part of a) frame etc. The maximumnumber of bits is computed through a rate adaptive algorithm because theobjective is to find the maximum number of bits that can be transmittedunder the given channel conditions. The inputs for this algorithm arefor example the signal to noise ratio level or SNR level per subcarrier,and the transmission power. The output for this algorithm is for examplethe maximum modulation order per subcarrier.

A sixth embodiment of the transmitter according to the invention asdefined in claim 7 is advantageous in that said algorithm furthercomprises a margin adaptive algorithm for computing a bit loading independence of an actual bit rate.

Said bit loading is calculated or not (by keeping the previous bitloading) dependently upon the channel conditions. Said actual bit rateindicates the actual number of bits per time slot or group of time slotsor (part of a) frame etc. This actual number will generally be smallerthan said maximum number due to segmentation rules. The bit loading iscomputed through a margin adaptive algorithm because the objective is tominimize the transmission power for the already known number of bitsunder the given channel conditions. The inputs for this algorithm arefor example the signal to noise ratio level or SNR level per subcarrier,and total number of bits to be transmitted. The output for thisalgorithm is for example the modulation order per subcarrier.

A seventh embodiment of the transmitter according to the invention asdefined in claim 8 is advantageous in that said transmitter comprises acode rate adapter for in response to a detection result of a real-timerequirement and to a further detection result of a target bit error rateadapting a code rate for said computing.

Said code rate is adapted to approach said target bit error rate. Afterthat, said bit loading can be computed, and code parameters can be set.The code rate adapter may form part of said processor system.

An eighth embodiment of the transmitter according to the invention asdefined in claim 9 is advantageous in that said transmitter comprises agenerator for in response to a detection result of a non-real-timerequirement and to a further detection result of a target bit error rategenerating a code rate and/or a block length and/or a number ofiterations and/or code parameters.

Said code rate and/or block length and/or number of iterations form anoptimum set generated via for example a look up table or a memory etc.and will imply a processing time smaller than a maximum tolerable delay.After that, said code parameters can be set. The generator may form partof said processor system.

Embodiments of the processor system according to the invention, of themethod according to the invention and of the processor program productaccording to the invention correspond with the embodiments of thetransmitter according to the invention.

These and other aspects of the invention will be apparent from andelucidated with reference to the embodiments(s) described hereinafter.

FIG. 1 illustrates in block diagram form a transmitter according to theinvention comprising a processor system according to the invention,

FIG. 2 illustrates a flow chart of a method according to the inventionfor the real-time situation, and

FIG. 3 illustrates a flow chart of a method according to the inventionfor the non-real-time situation.

The transmitter according to the invention forms part of a transceiver 1comprising an antenna interface 2 like for example a switch and/or aduplexer etc. of which an in/output is coupled to an antenna and ofwhich an output is coupled to an input of a first receiving interface 3like for example an amplifier and/or a filter etc. of which an output iscoupled to inputs of a first demodulator 4 and of a second demodulator5. An input of antenna interface 2 is coupled to an output of a firsttransmitting interface 6 like for example an amplifier and/or a filteretc., of which an input is coupled to outputs of a first modulator 7 andof a second modulator 8.

Transceiver 1 further comprises a connector interface 9 of which anin/output is to be coupled to an external unit like for example apersonal computer etc. and of which an output is coupled to an input ofa second receiving interface 10 like for example an amplifier and/or afilter and/or a demodulating unit and/or a decoding unit etc. An inputof connector interface 9 is coupled to an output of a secondtransmitting interface 11 like for example an amplifier and/or a filterand/or a modulating unit and/or a coding unit etc.

Transceiver 1 further comprises a processor system 20 comprising a firstdecoder 21 of which an input is coupled to an output of firstdemodulator 4 and of which an output is coupled to an input of secondtransmitting device 11. Processor system 20 further comprises a seconddecoder 22 of which an input is coupled to an output of seconddemodulator 5 and of which an output is coupled to an input of secondtransmitting device 11. Processor system 20 also comprises a first coder24 of which an input is coupled to an output of second receiving device10 and of which an output is coupled to an input of first modulator 7,and comprises a second coder 25 of which an input is coupled to anoutput of second receiving device 10 and of which an output is coupledto an input of second modulator 8. Processor system 20 comprises amemory 23, a communication interface 26 to be coupled to for example aman-machine-interface like for example a keyboard, a display, amicrophone, loudspeakers etc., and a controller 30.

Controller 30 comprises a processor 31 coupled to a coupler 39 like forexample a switch or a bus system, and comprises a first detector 32, asecond detector 33 and a selector 34 all coupled to coupler 39.Controller 30 further comprises a first coding interface 35 locatedbetween a control in/output of first coder 24 and coupler 39, a secondcoding interface 36 located between a control in/output of second coder25 and coupler 39, a first decoding interface 37 located between acontrol in/output of first decoder 21 and coupler 39, and a seconddecoding interface 38 located between a control in/output of seconddecoder 22 and coupler 39. Coupler 39 is further coupled to memory 23,to communication interface 26, to outputs of decoders 21 and 22 and theinput of second transmitting device 11, to the output of secondreceiving device 10 and the inputs of coders 24 and 25, and to controlin/outputs of demodulators 4 and 5, of antenna interface 2, and ofmodulators 7 and 8.

First coding interface 35 for example comprises a code rate adapter forin response to a detection result of a real-time requirement and to afurther detection result of a target bit error rate adapting code rates,and second coding interface 36 for example comprises a generator for inresponse to a detection result of a non-real-time requirement and to afurther detection result of a target bit error rate generating coderates and/or block lengths and/or numbers of iterations and/or codeparameters.

The transceiver 1 functions as follows. Packet data arriving at saidantenna flows via antenna interface 2 and first receiving interface 3 to(one of) said demodulators 4,5 for demodulation purposes and to (one of)said decoders 21,22 for decoding purposes, under control of controller30 (processor 31). Then, demodulated and decoded data flows via coupler39 to second detector 33 for detecting channel conditions and possiblyeither flows via coupler 39 to processor 31 for controlling purposes orto communication interface 26 for communication purposes and/or flowsvia second transmitting interface 11 to connector interface 9 forexternal purposes.

Packet data arriving via connector interface 9 flows via secondreceiving interface 10 and coupler 39 to first detector 32 and/or packetdata originating from the man-machine-interface arrives at communicationinterface 26 and flows via coupler 39 to first detector 32, undercontrol of processor 31, and is detected by first detector 32.

In response to a first detection result of a real-time requirement,selector 34 will select first coder 24 and first modulator 7 to be usedfor coding and modulation purposes. First coder 24 codes in accordancewith a first coding scheme comprising a convolutional code and firstmodulator 7 modulates in accordance with a first modulation schemecomprising an adaptive orthogonal frequency division modulation scheme(AOFDM). Said convolutional code and adaptive orthogonal frequencydivision modulation scheme allow the transmission of packet data havingreal-time requirements with improved efficiency.

In response to a second detection result of a non-real-time requirement,selector 34 will select second coder 25 and second modulator 8 to beused for coding and modulation purposes. Second coder 25 codes inaccordance with a second coding scheme comprising a turbo code andsecond modulator 8 modulates in accordance with a second modulationscheme comprising an orthogonal frequency division modulation scheme(OFDM). Said turbo code and orthogonal frequency division modulationscheme allow the transmission of packet data having non-real-timerequirements with improved efficiency.

Preferably, first detector 32 further detects a target bit error rateand/or a payload bit rate, to be able to improve/adapt said codingscheme and/or modulation scheme.

Processor system 20, in particular controller 30 and memory 23, more inparticular processor 31 and memory 23, can be used for runningalgorithms for improving/adapting said coding scheme and/or modulationscheme and/or for supporting the detecting of channel conditions and/orprocessing the channel conditions.

A first algorithm comprises a rate adaptive algorithm for evaluating amaximum available bit rate in dependence of said channel conditions.Said maximum available bit rate indicates the maximum number of bits pertime slot or group of time slots or (part of a) frame etc. The inputsfor this first algorithm are for example the signal to noise ratio levelor SNR level per subcarrier, and the transmission power. The output forthis algorithm is for example the maximum modulation order persubcarrier.

A second algorithm comprises a margin adaptive algorithm for computing abit loading in dependence of an actual bit rate. Said bit loading iscalculated or not (by keeping the previous bit loading) dependently uponthe channel conditions. Said actual bit rate indicates the actual numberof bits per time slot or group of time slots or (part of a) frame etc.This actual number will generally be smaller than said maximum numberdue to segmentation rules. The inputs for this second algorithm are forexample the signal to noise ratio level or SNR level per subcarrier, andtotal number of bits to be transmitted. The output for this algorithm isfor example the modulation order per subcarrier.

Said rate/margin adaptive algorithm and said (A)OFDM are of commongeneral knowledge to a person skilled in the art.

Via code rate adapter 35, in response to a detection result of areal-time requirement and to a further detection result of a target biterror rate, a code rate is adapted for said computing, to approach saidtarget bit error rate. After that, said bit loading can be computed, andcode parameters can be set.

Via generator 36, in response to a detection result of a non-real-timerequirement and to a further detection result of a target bit errorrate, one or more code rates and/or one or more block lengths and/or oneor more numbers of iterations and/or one or more code parameters aregenerated. Said code rate and/or block length and/or number ofiterations form an optimum set generated via for example a look up tableor a memory etc. and will imply a processing time smaller than a maximumtolerable delay. After that, said code parameters can be set.

The blocks in FIG. 2 have the following meaning:

-   Block 50: Detect the channel conditions.-   Block 51: Compute M (max. number of bits) through a rate adaptive    algorithm.-   Block 52: Define M.-   Block 53 : Detect real-time/non-real-time requirement.-   Block 54: Real-time ? Goto 56. Non-real-time ? Goto FIG. 3.-   Block 55: Detect target bit error rate.-   Block 56: Improve code rate in order to approach target bit error    rate.-   Block 57: Set code rate for branch 1 (real-time).-   Block 58: Define code rate.-   Block 59: Evaluate N (actual number of bits) in view of M.-   Block 60: Define N.-   Block 61: Compute the loading through a margin adaptive algorithm or    keep the old loading respectively dependently upon unstable or    stable conditions respectively.-   Block 62: Set loading for branch 1 (real-time).

In FIG. 2, the part above the dotted line is a so-called Media AccessController or MAC part, and the part below this dotted line is aso-called physical layer PHY. The part left of the dotted line is areceiving part for example at frame rate (for example for every packetreceived), and the part right from this dotted line is a transmittingpart for example for every portion of a frame.

The blocks in FIG. 3 have the following meaning:

-   Block 70: Detect the channel conditions.-   Block 71: Compute M (max. number of bits) through a rate adaptive    algorithm.-   Block 72: Define M.-   Block 73: Detect real-time/non-real-time requirement.-   Block 74: Real-time ? Goto FIG. 2. Non-real-time ? Goto 76.-   Block 75: Detect target bit error rate.-   Block 76: Generate the values for code rate(s), block length(s),    number(s) of iterations, select an optimum set.-   Block 77: Define code rate.-   Block 78: Evaluate N (actual number of bits) in view of M.-   Block 79: Define N.-   Block 80: Set code rate for branch 2 (non-real-time).

In FIG. 3, the part above the dotted line is a so-called Media AccessController or MAC part, and the part below this dotted line is aso-called physical layer PHY. The part left of the dotted line is areceiving part for example at frame rate (for example for every packetreceived), and the part right from this dotted line is a transmittingpart for example for every slot group.

FIGS. 1, 2 and 3 just show embodiments and do not exclude alternativesand/or possibilities not shown and/or mentioned. For example in FIG. 1,detectors 32 and 33 and selector 34 may be partly or entirely combinedand may be 100% software, 100% hardware or a mixture of both. Saidcoders 24 and 25 and rate adapter 35 and generator 36 may be partly orentirely combined and may be 100% software, 100% hardware or a mixtureof both. Said decoders 21 and 22 and decoding interfaces may be partlyor entirely combined and may be 100% software, 100% hardware or amixture of both. Modulators 7 and 8 may be partly or entirely combinedand may be made adaptable, and demodulators 4 and 5 may be partly orentirely combined and may be made adaptable. Further, each block showncan be separated into subblocks. Other blocks are not to be excluded.

For example in FIGS. 2 and 3, each block may be a (sub)step in themethod according to the invention and may be a (sub)function in theprocessor program product according to the invention. Each two blockscan be combined, especially per section (with both dotted lines creatingfour sections), and each block shown can be separated into subblocks.Again, other blocks (other substeps and subfunctions) are not to beexcluded.

So, many alternatives and/or possibilities can be made without departingfrom the scope of this invention.

1. Transmitter for transmitting packet data and comprising a detectorfor detecting packet data to be transmitted, characterized in that saidtransmitter comprises a selector for in response to a detection resultof a real-time requirement selecting a first coding scheme and a firstmodulation scheme for coding and modulating said packet data and for inresponse to a non-real-time requirement selecting a second coding schemeand a second modulation scheme for coding and modulating said packetdata.
 2. Transmitter according to claim 1, characterized in that saidfirst coding scheme comprises a convolutional code and said firstmodulation scheme comprises an adaptive orthogonal frequency divisionmodulation scheme and said second coding scheme comprises a turbo codeand said second modulation scheme comprises an orthogonal frequencydivision modulation scheme.
 3. Transmitter according to claim 2,characterized in that a further detection result comprises a target biterror rate and/or a payload bit rate.
 4. Transmitter according to claim3, characterized in that said transmitter comprises a further detectorfor detecting channel conditions.
 5. Transmitter according to claim 4,characterized in that said transmitter comprises a processor system forrunning an algorithm.
 6. Transmitter according to claim 5, characterizedin that said algorithm comprises a rate adaptive algorithm forevaluating a maximum available bit rate in dependence of said channelconditions.
 7. Transmitter according to claim 6, characterized in thatsaid algorithm further comprises a margin adaptive algorithm forcomputing a bit loading in dependence of an actual bit rate. 8.Transmitter according to claim 7, characterized in that said transmittercomprises a code rate adapter for in response to a detection result of areal-time requirement and to a further detection result of a target biterror rate adapting a code rate for said computing.
 9. Transmitteraccording to claim 7, characterized in that said transmitter comprises agenerator for in response to a detection result of a non-real-timerequirement and to a further detection result of a target bit error rategenerating a code rate and/or a block length and/or a number ofiterations and/or code parameters.
 10. Processor system for use in atransmitter for transmitting packet data and comprising a detector fordetecting packet data to be transmitted, characterized in that saidprocessor system comprises a selector for in response to a detectionresult of a real-time requirement selecting a first coding scheme and afirst modulation scheme for coding and modulating said packet data andfor in response to a non-real-time requirement selecting a second codingscheme and a second modulation scheme for coding and modulating saidpacket data.
 11. Method for transmitting packet data and comprising thestep of detecting packet data to be transmitted, characterized in thatsaid method comprises the step of in response to a detection result of areal-time requirement selecting a first coding scheme and a firstmodulation scheme for coding and modulating said packet data and of inresponse to a non-real-time requirement selecting a second coding schemeand a second modulation scheme for coding and modulating said packetdata.
 12. Processor program product for use in a transmitter fortransmitting packet data and comprising the function of detecting packetdata to be transmitted, characterized in that said processor programproduct comprises the function of in response to a detection result of areal-time requirement selecting a first coding scheme and a firstmodulation scheme for coding and modulating said packet data and of inresponse to a non-real-time requirement selecting a second coding schemeand a second modulation scheme for coding and modulating said packetdata